Hello members of TechNet, We use IGBTs in TO-247 packages and diodes in TO-220 packages mounted to heatsinks using a spring steel clip. There is a great deal of discussion regarding the amount of pressure the clip puts on the device (or lack of pressure), what size fastener to use to mount the clip and how tight the fastener should be. We are currently using a spring clip made by AAVID which when "tightened" we find that the tab the screw goes through does not sit flush with the heatsink. I need info on recommended screw sizes, screw torques, and pressure applied to the devices to produce proper thermal transfer. How much pressure on the device is enough? What is my best way to measure the force to prove the assemblies are working to Engineering's satisfaction? Thanks in advance for your help. Phil Nutting Manufacturing Engineer Kaiser Systems, Inc. 126 Sohier Road Beverly, MA 01915 ph: 978-922-9300 fx: 978-922-8374 [log in to unmask] ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################